1. Field of the Invention
The present invention relates to a fuel cell such as a direct methanol fuel cell (DMFC) that uses a fuel, for example, methyl alcohol or methanol, and also concerns an electronic device, a portable terminal and a camera that are provided with such a fuel cell.
2. Description of the Related Art
The direct methanol fuel cell is a fuel cell of a type in which methanol (CH3OH) mixed with water is directly supplied to a fuel electrode with oxygen being supplied to an air electrode in order to obtain electric energy via an electrolyte membrane such as a proton conductive membrane. Here, in the direct methanol fuel cell, carbon dioxide (CO2) is generated by a catalytic reaction of the fuel electrode as a by-product and water (2H2O) is generated by a catalytic reaction of the air electrode as a by-product. Moreover, the amount of consumption of the fuel, i.e., methanol, stored in a fuel chamber, is detected by using, for example, a method for detecting the change in color density of a pigment sealed in a recovery bag in which the by-product is recovered (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2003-36879).
The above-mentioned methanol is a transparent colorless liquid, and is soluble to water or the like. Moreover, the methanol is poisonous to the human body, and even a dose of 8 to 10 g of methanol normally causes loss of one's eyesight, and a fatal dose is considered to be 20 to 100 g. For this reason, it is necessary to prevent people from drinking a fuel such as methanol by mistaken for water or the like. It is also necessary to prevent a different kind of fuel from being refueled by mistaken it as methanol.
In a fuel cell disclosed in JP-A No. 2003-36879, since the fuel is used as a transparent colorless liquid as it is, there is a danger of refueling a different kind of fuel by mistaken it as methanol as described above.
Moreover, it is difficult to conduct a visual detection based upon the color density, and requires a detection sensor, resulting remaining amount detection mechanism to be large-scaled.